The radio (or wireless) telephone having separable base and handset is extensively used since the user is free from being unnecessarily unduly confined to a reletively limited space. In use, the handset, however, will be noised when:
1) The handset is out of range; PA0 2) The base has a power failure or an interrupted power; or PA0 3) There exists a noise source.
As shown in FIG. 1, there is shown a conventional radio telephone in which the base includes a power-stabilizing circuit 11, a digital controller or central processing unit (CPU) 12, a radio frequency transmitting module 13 including a transmitting driver 131 and a transmitting amplifier 132, a transmission signal processor 24, a transmission data processor 25, a receiving data processor 26, a receiving signal processor 27 and a receiver 28. Likewise, the handset includes a receiver 14, a receiving signal processor 15, an amplifier 16, a speaker 17, an antenna 18, a receiving data processor 19, a transmitting amplifier 20, a transmitting driver 21, a transmission signal processor 22, a transmission data processor 23, a digital controller or CPU 191, a display 192 and a keypad 193.
Upon power failure or interruption of the base, there is no signal transmitted from radio frequency transmitting module 13. Nevertheless, the handset is still powered on which means that receiver 14, receiving signal processor 15 and audio amplifier 16 are still in a working mode through which any signal including a noise can transmit to speaker 17 which will sound to the user only the unpleasant amplified noise since the carrier wave has disappeared through the power failure or interruption of the base. As described above, there are three noise sources. The user will be bothered to inevitably try to redial the telephone in vain if he or she is not able to quickly get alert to the fact the base is suffering from a power failure or interruption.
It is therefore tried by the applicant to deal with the above situation, i.e. the base has a power failure or an interrupted power, encountered by the prior art.